C++ Stacks

C++ Stacks: Last-In, First-Out (LIFO)

A Stack is an incredibly important data structure in computer science. It operates on the LIFO (Last-In, First-Out) principle.

Think of a stack of pancakes: the last pancake you place on top of the stack is the very first one you eat!

1. Stack Operations

The C++ STL provides the <stack> library, which gives you access to the following core methods:

• .push() - Adds an element to the top of the stack.
• .pop() - Removes the element from the top of the stack.
• .top() - Returns the value of the top element without removing it.
• .empty() - Returns true if the stack is empty.
• .size() - Returns the number of elements in the stack.

#include <iostream>
#include <stack>
using namespace std;

int main() {
  stack<string> webHistory;
  // User visits three pages
  webHistory.push("Google.com");
  webHistory.push("GitHub.com");
  webHistory.push("IntricateDevo.com");
  // The top element is the last one visited
  cout << "Currently viewing: " << webHistory.top() << "\n";
  // User clicks the 'Back' button on their browser
  webHistory.pop();
  // Now the top element is GitHub
  cout << "Went back to: " << webHistory.top() << "\n";
  return 0;
}

2. Practical Uses of Stacks

Stacks are used everywhere in software engineering:

• Undo/Redo Mechanisms: In text editors, your actions are pushed to a stack. Hitting Ctrl+Z pops the last action!
• Browser History: Navigating "Back" uses a stack.
• Function Calls: Compilers use a "call stack" to keep track of function executions.